Prior art refractory presses commonly include a rigid frame having a mold table supported by the frame for vertical movement. An example of a typical prior art refractory brick press is illustrated in the Dorsey U.S. Pat. Nos. 3,447,205 and 4,265,610. In such brick presses the mold table fixedly supports a mold box having a plurality of vertical mold cavities, and a lower plunger assembly is fixed to the frame and includes a plurality of plungers adapted to project upwardly into the mold cavities. Such presses also commonly include an upper plunger assembly including a plurality of downwardly extending plungers, and a ram is provided to cause downward movement of the upper plunger assembly so that refractory material in the mold cavities can be compressed between the upper and lower plungers.
One of the effects of having fixed lower plungers and compression by the upper plungers is that the density of the resultant compressed refractory material tends to be greater in some parts of the brick than in other parts of the brick.
It is common that the mold cavities of mold boxes employed in refractory presses have a depth of twelve to sixteen inches, whereas the brick to be formed may be only three inches in thickness. It will be appreciated that compression of the refractory material results in wear of the walls of the mold cavity and that this wear is particularly significant in the area where the pressure on the refractory material is the greatest. Accordingly, in many prior art presses the wear of the mold cavities is not uniform and the mold boxes tend to wear in the specific area where the finished brick is formed.